In the first systematic review and meta-analysis of trends in sperm count, researchers from the Hebrew University of Jerusalem's Faculty of Medicine and the Icahn School of Medicine at Mount Sinai report a significant decline in sperm concentration and total sperm count among men from Western countries. A rigorous and comprehensive meta-analysis of data collected between 1973 and 2011 finds that among men from Western countries who were not selected on the basis of their fertility status, sperm concentration declined by more than 50%, with no evidence of a “leveling off” in recent years. These findings strongly suggest a significant decline in male reproductive health that has serious implications beyond fertility and reproduction, given recent evidence linking poor semen quality with higher risk of hospitalization and death. Research on causes of this ongoing decline and their prevention is urgently needed.